Offshore oil rigs can provide prime fish habitat

But will California's platforms stay in the ocean once the oil runs out?

 

Most of the time, human infrastructure and wildlife mix about as well as seabirds and plastic. Our highways carve up animals’ habitat. Our dams block them from spawning grounds. Our solar plants scorch them into charcoal briquettes.

Yet the natural and manmade environments are spectacularly compatible in one unlikely instance: the 27 offshore oil rigs that dot the California coastline. The state’s drilling platforms may be unsightly — not to mention responsible for one of the worst environmental disasters in American history — but according to a new study, they might provide the best marine habitat in the world.

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Believe it or not, California's oil rigs might provide some of the world's best marine habitat. Photo courtesy of the Bureau of Safety and Environmental Enforcement.

To understand why, it helps to know something about rockfish, one of the West Coast’s most economically important groups of fish. “Rockfish are what’s called demersal fish — they’re associated with the bottom,” says Jeremy Claisse, a postdoctoral researcher at Occidental College. “They want places to hide and shelter, to hunt food.” But the seabed in the deep waters off California doesn’t offer much of the hard, complex substrate that rockfish require.

Enter the state’s offshore rigs, whose massive lattices provide outstanding rockfish habitat. Juvenile and larval fish — which otherwise would likely perish in the vast expanse of the open ocean — settle high in the structures. As the fish grow, they head for deeper waters closer to the base of the structures, which range from 150 to 650 feet tall. “The first thing anyone — trained scientist or casual recreational diver — notices around a rig is the big fish, lots of them,” ichthyologist Milton Love told Pacific Standard in 2010. 

Over the course of more than 15 years, Love and other researchers used submersibles to survey fish at 16 different platforms. When Claisse and colleagues crunched that data, they were surprised to discover that, by one standard, California’s oil rigs — not the estuaries of Louisiana, not the coral reefs of Moorea, not the seagrass beds of Australia — are the most productive marine habitats ever recorded. And by an order of magnitude, too. “We knew they were very productive, but we didn’t realize how high it was going to be compared to other habitats,” Claisse says.

How California will use this and similar studies remains to be seen. No one who remembers the flaming wreck of the Deepwater Horizon would suggest that “drill, baby, drill” is the best strategy for benefiting sea creatures — and indeed, the Obama administration has imposed a moratorium on new drilling along the Pacific Coast.  But the state’s coast is already peppered with rigs, most of them slated for decommissioning once the hydrocarbons run dry.

Rockfish school near a California drilling platform. Photo courtesy of Donna Schroeder, Bureau of Ocean Energy Management.

Under current federal law, energy companies have to completely remove rigs at the end of their lifespan. In the Gulf of Mexico, however, where offshore oil structures abound, a program called “Rigs-to-Reefs” allows companies to simply lop off the top of the platform and leave behind the support struts. The deal saves oil companies millions in deconstruction costs; the companies then typically give part of their savings back to the state. In 2010, California passed AB 2503, its own version of rigs-to-reefs, which would allow partial removal on a case-by-case basis. No rigs have been decommissioned in the intervening years, so the law hasn’t been put to the test — yet.

Not every Californian is sanguine about the rig-to-reef concept. "It's just an opportunity for the oil companies to renege on their commitments to clean up these sites when they were first allowed to install the platforms," Linda Krop, Chief Counsel at the Santa Barbara-based Environmental Defense Center, told KPBS public television this summer. Mounds of sludge and debris that accumulate at the base of rigs have been found to contain toxic chemicals and heavy metals. UCLA’s Environmental Law Center graded the law a C–.

Whatever the fate of California’s rigs, Claisse says the same principles that make offshore drilling platforms high-quality habitat could be baked into the design of future ocean energy infrastructure, namely wind and tidal turbines. “Renewable energy structures have longer lifespans than oil platforms, which are only there for as long as they’re extracting fossil fuels,” he says. “There’s an opportunity to put out structures that maximize fisheries and conservation benefits, even if that’s not their primary purpose.”

Ben Goldfarb is a correspondent at High Country News.

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